Klein Mantra rebuild / TSDZ2

[izeman]

As some of you, that are here for more than 5 years, may remember, I build a Klein Mantra with a HS3540 and some A123 pouch cells in a big container at the handle bar. That bike was some kind of fun, but on the other hand not very useable and handled quite strange.

So i decided to rebuild it, and install a small battery and a small TSDZ2 with it's great alternative firmware. And the more I do the more things need to be done

This is what the bike looked before:





What will be done:

.) New battery (saddle bag), MUCH smaller then before from LiFePo4 22s 30Ah to 14s 9Ah
.) New tires. The ones installed are nice, but 8 years old now and not really soft anymore
.) New brakes. The Avid Elixir 3 were nice some years ago, but they will be replaced by Shimano XT 8100
.) New hubs. New centerlock discs require new hubs, and as the DD in the back goes, it needs a new hub anyway, Shimano XTs as well
.) New motor. The small TSDZ2 with 500/750W will be installed, a middrive which is now really a bike, and not a moped
.) Cranks will be shortened. As the bike has 20" rims, 170mm cranks touch the ground too often

 

[izeman]

I bought the motor from pswpower.com and was shocked/impressed how super tiny it is. This really is a 500W motor. No way to hot rod it. This is for helping you to pedal, and you need to do your exercise.
Unfortunately my self built rear frame part was tailor made for the last bottom bracket, and the new motor didn't fit. I had to remove some material inside to widen it. Used a file, a dremel, sand paper. Nothing did help. Luckily i had ordered one of those "big dremel" tools from China some weeks ago, and with the right tool it was 30min of grinding to make the motor fit.


View attachment 1

 

[izeman]

The battery at the handle bars was not ideal, and made the bike very head heavy. And it's not needed for the small motor anyway.
I looked a lot for a big saddle bag to install the battery into. Of course the space is limited, and needs some support (other then the velco straps) to be properly mounted to the saddle.
42 cells is the maximum I can fit into any reasonably sized bag. I measured and designed in Fusion to make a battery spacer/holder, and it's a super nice fit. I still don't know how to do the wiring/cell connection to have a proper and even current flow. Cells used will be LG HG2 3000mAh ordered from nkon.nl as always. Genuine cell for a reasonable price.
Cells seen in the picture are old cell for illustraion only. They will not be used
The BMS will be one of the well known and good working BT smart BMS: https://www.aliexpress.com/item/32794186005.html?spm=a2g0s.9042311.0.0.13f64c4d2YBneB I chose the 30A version, as the motor will see 18A max and the FETs of the the BMS will most probably be replaced by genuine IRFB 3077 which can handle much more current and will keep the BMS super cool even if fully covered in heat shrink.








View attachment 1

 

[izeman]

Next step was the rear frame. It was never designed for a mid drive, and so the straight rod on the right side was touching the motor, making it impossible to mount. I could have turned a spacer, but that would have moved the motor even more to the right, and a straight chaín line is almost impossible even with the motor properly mounted.
I decided to cut the frame as it's steel anyway and easily weldable. There was also an additional support welded to the frame, where the motor will be fixed to, so it can't turn inside the bottom bracket.








A lot of grinding and sanding later it looks perfectly fine now, ready to be painted.


View attachment 1


This is a picture of the little bracket i made to screw down the motor. The original bracket was a bit to wobbly for my liking. This is rock solid now.

 

[Tommm]

Don't go centrelock. They are a lot more expensive and no cheap alternatives. I would easily choose a different hub if I had to, proprietary standards suck.

 

[izeman]

Don't go centrelock. They are a lot more expensive and no cheap alternatives. I would easily choose a different hub if I had to, proprietary standards suck.

I already ordered centerlock hubs and discs. There weren't many choices for 6 hole hubs & discs. Having not ordered brake stuff for quite some time I thought centerlock was the new standard.

 

[izeman]

There seems to be massive interest in this build based on the comments and replies , so I want to give a short update.
Building the battery started now.
After having printed the battery spacer, and ordered 42 LG HG2 batteries it was time to think about the nickel tabs to combine it into one big battery. The challenge was to make sure that at least two cells are connected laying next to each other. I will try and use 0.2mm 100% pure nickel strips.
The serial connection will have at least 35mm length and 0.2mm height. This makes it 35 x 0.2 = 7mm2 which is about 1.75mm2 copper equivalent. More than enough for 18A max.

This is how the cells will be connected. If you got any input or ideas for improvement, please let me know:

 

[madin88]

This is how the cells will be connected. If you got any input or ideas for improvement, please let me know:

Looks fine :thumb:

Don't go centrelock. They are a lot more expensive and no cheap alternatives. I would easily choose a different hub if I had to, proprietary standards suck.

I already ordered centerlock hubs and discs. There weren't many choices for 6 hole hubs & discs. Having not ordered brake stuff for quite some time I thought centerlock was the new standard.

If you don't want to stay with centerlock you could buy an adapter for 6-hole discs.

 

[Wolfeman]

Cool project, looking forward to seeing more updates. Thanks for posting.

 

[izeman]

Some updates:

I installed a temperature sensor

 

[izeman]

The frame was sanded and painted in the same mate black as the original frame.

 

[izeman]

Yesterday I started building the wheels. They looks quite beefy as they are only 20" rims with moped tires. I really like the look of them

 

[Bigwheel]

Super Nice! What’s your plan to get the higher gear ratios necessary for 20” wheels?

 

[izeman]

Super Nice! What’s your plan to get the higher gear ratios necessary for 20” wheels?

That's a good point I'm not sure about. I ordered the biggest front sprocket it could find which is a 52T. This is 24% more than the regular 42T. The circumfence of the 20" with the moped tire is 172cm compared to 216cm of a regular MTB tire. That's 25% more. So it should be almost exactly the same that way.

I also shortened the cranks because of the lowered bottom bracket. I rode this setup with standard 170mm cranks before and i hit the road quite often in sharp corners. The cranks were shortened by 30mm to 140mm. That's quite short for a tall guy (192cm) like me, and you loose power with shorter lever arm, but it will help with high cadence.

 

[izeman]

Today was battery building day. All nickel plates have been cut before, so I only had to install the paper rings on the positive pole, and put them into the printer holders, taking care of the right order.

Nickel used was 0.15 pure nickel from nkon. Where I couldn't use one single plate I welded a second one on top. Welding time was 7msx3 instead of 5msx2 for the single sheets.

I also installed the two temperature sensors that come with the smart BMS. Their wires are routed between the cells. The only thing that I'm a little concerned about. Even though this is is a VERY sturdy and compact build, and the cells can't move, the wire in between the cells COULD potentially cause a short. I suspect this change to be minimal, but who knows. What do you think? Let me know your thoughts.

Here are some pics. The positive and negative wire were pre-soldered to the plates and then the nickel was welded to the cells to avoid heat transfer. Well, after I welded it I had to turn on of the positive wires a little bit and re-soldered it. But this was very quick, and I hope save.

 

[izeman]

Wrapped in Kapton tape and checked with the smart BMS. Everything is quite in balance.

 

[izeman]

After I ordered the third brake adapter which didn't fit, I decided to build my own.
What for do I have a mill?

 

[izeman]

Also ordered an Alfine 11 to get a straighter chain line, and enjoy 409% of bandwidth.
Now I need to wait for the new spokes, as the wheel is already laced.
Unfortunately the Alfine gear shifter and the XT 8100 lever don't really go together. I'm not sure if I can shift with it or need to 3D print something that makes the lever longer.

Here are some pics. Maybe anyone got an idea how to deal with it. I got large hands, so maybe it's doable.

 

[izeman]

It rolls. I may swap the 52T front ring for the original 42T one, as it's geared too high to my feeling. 16T in the back. The Alfine 11 is super nix. Adds some drag and is NOT as easy to pedal as a "regular geared" setup, but being able to shift gears at a stand still and having an almost perfect straigh chain line makes it worth it.

 

[casainho]

Super Nice! What’s your plan to get the higher gear ratios necessary for 20” wheels?

I also shortened the cranks because of the lowered bottom bracket. I rode this setup with standard 170mm cranks before and i hit the road quite often in sharp corners. The cranks were shortened by 30mm to 140mm. That's quite short for a tall guy (192cm) like me, and you loose power with shorter lever arm, but it will help with high cadence.

So the pedal human power calculations on our OpenSource firmware will now be wrong because they consider the 170mm cranks. In future I will make this length as a configuration on the screen as all the others already available.

And what is that red thing to hold the temperature sensor?

And very nice build!!

 

[izeman]

Sure. You're right. Haven't thought about that. But different crank lenght means different power.
That's also the reason i asked for a higher cadence version. You pedal much faster with shorter cranks.

The red stuff is high temperature automotive silicone.

K2 Hochtemperatur Silikon, Dichtmasse, Dichtsilikon, hochtemperaturbeständig bis +350°C, rot, 85g https://www.amazon.de/dp/B00GFACX1I/ref=cm_sw_r_cp_api_i_aBDAEbR10JN94